Streptococcus sanguis and S. mitis are among the earliest organisms to colonize the tooth surface and remain the majr organisms of dental plaque. Studies have shown that these organisms adhere specifically to saliva coated tooth surface as well as interacting specifically with other oral bacteria, e.g., Actinomyces viscosus, S. mutans and Bacterionema matruchotii. Thus S. sanguis and S. mitis may play a pivotal role in plaque formation and its sequelae, caries and periodontal disease. The interactions with saliva as well as with other bacteria are mediated through bacterial surface receptors. Studies of the serology of these organisms indicate a relationship between the degree of adherence as well as the type of adherence and the presence of specific antigens in the surface. Recent studies also indicate that both the quantity and perhaps even the kinds of surface polymers present in a bacterial cell may be regulated by the environment. This could create the interesting situation in which the regulation of surface polymers which interact with the environment are themselves under environmental control. Observations made in continuous culture systems in which environment can more readily be manipulated, indicate that at more rapid growth rates, cells become more adherent. The surface changes associated with this increased adherence have not been explored. The objectives of the proposed studies is to determine the affect of growth rate, substrate and pH on these surface polymers and the associated biological activities, i.e., adherence, salivary aggregation and interbacterial interactions. These studies will employ a chemostat to establish an open system more closely resembling in vivo growth. Both the extracellular polymers as well as the cell surface associated polymers responding to environmental influence will be surveyed using two dimensional rocket immunoelectrophoresis and polyacrylamide gel electrophoresis. Once identified the polymers will be isolated and characterized chemically and immunochemically and their relationship to properties involved in plaque formation determined. Knowledge of these polymers and how they are controlled and interact with the environment is necessary in designing strategies to control plaque formation and its sequelae, caries and periodontal disease.